A novel method of forming chromogenic photographic images, wherein conventional development processes comprising both aqueous development and dry thermal development are utilized in combination with substantially dry thermally activated transfer of the resulting dye images to a polymeric receiver layer has been described by Willis and Texter in U.S. Pat. No. 5,270,145. A substantial improvement in the imaging system, as disclosed by Bailey, Texter and White, U.S. patent application Ser. No. 08/804,868 filed Dec. 6, 1991; Bailey, Texter and White, U.S. patent application Ser. No. 08/073,821 filed Jun. 8, 1993; Bailey and Mura, U.S. patent application Ser. No. 08/073,825 filed Jun. 8, 1993; Bailey and Mura, U.S. patent application Ser. No. 08/073,822 filed Jun. 8, 1993; Bailey, Mura and Eiff, U.S. patent application Ser. No. 08/073,826 filed Jun. 8, 1993 and Bagchi and Bailey, U.S. patent application Ser. No. 08/159,022 filed Nov. 29, 1993, is obtained by the addition of certain materials to one or more of the layers that constitute the imaging element.
The essential morphology of such an imaging system is illustrated in FIG. 1. This imaging element consists of, for example, a conventional chromogenic photographic multilayer imaging element coated on a polymeric receiver element. The conventional imaging element (hereafter image originating element or donor layer) consists of one or more imaging layers, optionally one or more interlayers and one or more protective layers (layers 1,2, . . . , N in FIG. 1) Any or all of these layers may contain the dye-diffusion transfer facilitating materials described in the aforementioned patents and applications, but in particular these materials may be incorporated in the silver halide imaging layer. The polymeric receiver layer consists of one or more layers of the same or different materials. The receiving layer is coated on the appropriate transparent or reflective base. The image originating element is coated on the polymeric receiver element with an optional intervening stripping layer. The images are created by conventional radiation sensitivities in the silver halide emulsion containing layers, and these images are amplified using development processes well known in the art. After development, the development is stopped by appropriate means, and the element is dried. No fixing or bleaching chemistry is invoked in this process. After the elements have been dried, they are subject to heating in order to transfer the image dyes to the receiver layer. After such an image transfer process, the donor layers are separated from the dye receiver layer. The receiver layer and supporting base is retained as the final image element. The donor layer, containing the silver, silver halide and fine organic chemicals associated with the imaging process is available for recycling. These inventions thus reduce the amount of waste material generated in the photographic development process by not employing any bleach, fix or bleach-fix (blix) chemistry and makes available the conventionally retained organic chemicals for efficient recycling.
Dye sensitized silver halide emulsions can be subject to substantial unsensitization, the desorption of spectral sensitizing dyes from silver halide, which results in a loss in photographic sensitivity in the presence of certain materials that are incorporated in an imaging layer of chromogenic imaging elements. Substantial efforts can be expended in materials modifications or process optimizations in order to solve the problem of unsensitization in dye sensitized silver halide imaging elements.
It is well known in the art that melts containing dye-sensitized silver halide emulsions and coupler dispersions that show melt-hold unsensitization can be successfully coated with improved sensitometric characteristics by mixing individual melts of the dye sensitized silver halide emulsion and the coupler dispersion at some shorter time prior to coating. Continuous processes that mix the incompatible melts at a common junction prior to delivery to the coating hopper, known as dual-melt coatings, are well known.
Collins and Wellford, in U.S. Pat. No. 2,912,343 issued Nov. 10, 1959 disclosed the method of producing color photographic elements comprising a dye sensitized silver halide emulsion and the color coupler or other components that tend to reduce the sensitivity of the emulsion over time by controlling the time between mixing and coating. In particular Collins and Wellford disclose the use of an in-line active mixing means to continuously coat a red dye sensitized photographic element containing the cyan coupler, 1-hydroxy-2-naphthoyl-stearylamine-4-sulfonic acid sodium salt.
In-line mixing of liquids is well known in many chemical technologies as is described in various sources including a chapter on mixing and blending by Oldshue and Todd in the "Kirk-Othmer Encyclopedia of Chemical Technology", 3rd Ed., vol. 15 Wiley-Interscience, New York, 1981 and references cited therein.
An alternate means of controlling the solution contact time between incompatible materials is achieved by intimate mixing of solid particles followed by continuous or on-demand liquefaction of the solid mixture prior to coating.
Apparatus to continuously liquefy the photographic melts are disclosed in French Patent 2,111,176 assigned to Agfa-Gevaert, filed May 8, 1972 and French Patent 2,277,360 assigned to Agfa-Gevaert, filed Jul. 4, 1975 and by Ichikawa et al. in German Patent 3406600, filed Feb. 23, 1983 and by Eaton, Toner and Wooster in U.S. Pat. No. 5,191,910. Kresinske, Winkler and Possanza, U.S. patent application Ser. No. 08/163,245 filed Dec. 6, 1993, discloses an apparatus and method for on-demand liquefaction of solid chunks of aqueous gelatin melts.
Le Faou and Hervieux, International Patent Application WO 89/06829 filed Jan. 18, 1989, disclosed a process for obtaining silver halide photographic compositions from individually prepared melts that are chill chunked and cold mixed then liquefied just prior to introduction to the coating station.
All of these aforementioned methods achieve some control over the solution contact time between the dye-sensitized silver halide emulsion and the potentially sensitometrically deleterious material in another melt.
The methods and materials for chemical sensitization of silver halide emulsions are well established in the art of photography. Numerous reviews and summaries of the techniques and materials and the photographic consequences of chemical sensitization have been published including "The Theory of the Photographic Process, 4th Ed.", Chapter 5, edited by T. H. James and published by Macmillan Publishing Co, New York (1977). A particular example of chemical sensitization disclosed, for example, by Davey and Knott in U.S. Pat. No. 2.592,250 (Apr. 8, 1952) is termed halide conversion. This consists of treating the completed emulsion with an alkali halide solution capable of forming a less soluble silver salt than the original silver halide emulsion. In the case of silver chloride emulsions subsequently treated with a doctor solution of alkali bromide as described, for example, by Deaton in U.S. Pat. No. 5,049,485 there is advantageously obtained improvements in stability to development fog and in spectral sensitizing dye adsorption as disclosed in Research Disclosure, Issue 176, Item No. 18716 (November, 1979).